Aqueous composition containing polyvalent metal salt of an acidic copolymer as a thickener



United States Patent Q 3,826,281 AQUEOUS COMPOSITION CONTAINING POLY-VALENT METAL SALT OF AN ACIDIC COPOLY- MER AS A THICKENER Richard E.Barren, Levittown, and Victor Runowicz, Philadelphia, Pa, assignors toRohm & Haas Company, Philadelphia, Pa., a corporation of Delaware NoDrawing. F iied Feb. 4, 1957, Ser. No. 637,875 6 Claims. (Cl. 260-2943)This invention relates to aqueous synthetic polymer dispersions adaptedto be used for coating purposes and especially to pigmented systems ofthis type used as waterbase paints. The invention also concerns methodsof preparing such systems.

Aqueous coating systems using casein as the binder have long been knownand have been used to form waterbase paints. However, the use of caseinand related proteinaceous materials in aqueous coating systems hascertain disadvantages, one of the most important of which is thetendency to putrefaction and another is the sensitivity of the coatingsto Water. Because of these properties, if for no other, resort hasrecently been had to the use of synthetic linear polymers such aspolymers of vinyl acetate and of acrylic esters as the binders in suchaqueous coating compositions. Various thickening agents have been usedto render such aqueous dispersions of the synthetic polymers of suita leviscosity for application either by spraying or brushing. The terms flowand leveling are qualitative terms which refer to the character of theaqueous system in respect to its ability to be applied as by brushingand to flow in such a manner over the substrate as to avoid excessiveshowing of brush marks, or to assure a complete absence thereof afterdrying.

In the making of emulsion polymer coating compositions there aregenerally two types of thickeners used. One type is a water-solublepolymeric thickener which increases the viscosity of the dispersion byproducing a structure due to limited aggregation or flocculation ofdispersed particles. Such flocculated systems are pseudoplastic incharacter in that the will reduce in viscosity on application by brushor roller, but they have the characteristic of building up rapidly inviscosity on cessation of shear so that good dew and leveling are notachieved. In some cases, if a suflicient quantity of a watersolublepolymeric thickener is used, the polymer dispersion can be re-dispersed(from a flocculated condition) so that good flow and leveling can beachieved through the elimination of thixotropic character, but when thisis done the coatings that are obtained from the system arewater-sensitive.

The second type of thickener generally used includes the so-calledhydrated colloids, such as treated bentonites, which increase theviscosity of the system not by flocculating the dispersed particles butsimply by becoming swollen in the presence of water. The viscosity thatis obtained is also of thixotropic character with very short recoverytime (that is, recovery from a thin system during shearing to a thicksystem on cessation of shear). The available thickeners usually operatein one of the two ways mentioned above butsometimes they may operate inboth ways together. Thus, some naturally-occurring thickeners, such ascasein, alginates, or cooked starch, may operate in both ways describedhereinabove. In aqueous polymeric systems, good how and leveling prop-3,026,281 Patented Mar. 29, 1952 ertics are sometimes obtained with suchcommon thickening agents as methyl cellulose. However, in many of theaqueous systems [formed with linear polymeric resin binders, the knownthickening agents do not provide good flow and leveling. While theselatter polymer systems using known thickening agents in the formulationof paints may sometimes provide adequate flow and levelingcharacteristics for application to textured or rough surfaces where thetexture or roughness hides or masks the brush marks or otherirregularities of the coatings, nevertheless, on smooth surfaces, theselatter resin formulations using the known thickeners show brush marksexcessively.

it is an object of the present invention to provide a thickener which issubstantially free of aggregating or flocculating action but yetprovides a thixotropic character with a reason-ably long recovery timeso that good flow and leveling are obtained. Another object is toprovide a new aqueous coating composition comprising a dispersedwater-insoluble linear addition polymers and a. thickening agent whichhas improved flow and leveling qualities Whether or not a pigment isemployed in the system. it is a further object of the invention toprovide an improved aqueous acrylic polymer dispersion havingoutstanding fiow and leveling characteristics. Another object of theinvention is to provide aqueous linear polymer dispersions ofthixotropic character wherein the recovery time is suficiently long toprovide good flow and leveling. Other objects and advantages of theinvention will be apparent from the description hereinafter.

The new aqueous polymer dispersions of the present invention comprise(l)a binder which essentially comprises or consists exclusively ofWater-insoluble synthetic linear polymeric material, and (2) athickening agent formed of a certain class of poly-anionic material inconjunction with polyvalent metal ions.

Heretofore, in the making of coating compositions of aqueous dispersionsof water-insoluble addition polymers, the introduction of polyvalentmetal ions has generally been avoided because of the severe loss instagility such additions caused including increased settling andprecipitation, and especially the loss of freeze-thaw stability evenwhen special care is exercized in the choice of emulsifiers.Surprisingly, it has been found that the polyvalent metal ions can beintroduced into such aqueous dispersions in large amounts withoutreducing the stability below practical limits provided the polyanionicmaterial described herein is introduced properly in conjunction with thepolyvalent metal. An essential requirement is that the polyanion beintroduced into the dispersion in the form of a water-soluble orself-dispersible salt; otherwise, no appreciable thickening is obtainedin the pre ence of the polyvalent metal ion. The polyanion must also bewithin a certain molecular weight range, sufiiciently high to result ina marked thickening action in the aqueous system and yet not so high asto be precipitated as distinct particles or agglomerates by thepolyvalent metal ion. The molecular Weight is selected to provide forthe formation of a gelatinous polyvalent metal salt of the polyanion inthe aqueous phase of the system that is of essentially continuouscharacter.

The polyanionic material, which for convenience may be called apolyanion, is a water-soluble salt, such as an ammonium or an alkalimetal salt, of a polymeric compound of either addition or condensationtype containing a plurality of sulfuric acid, sulfonic acid, orcarboxylic acid groups. In conjunction with a polyvalent metal ion, thepolyanion thickens the aqueous system without aggregating orflocculating the dispersed particles, such as of the binder polymer, thepigment when present, and so on. The polyanion contains suficient acidgroups to become soluble in water when at least partially neutralized byammonium hydroxide, an alkali metal base, or a watersoluble amine, suchas methylamine, diethylamine, triethylamine, monoethanolamine, etc. Itis believed that the polyvalent metal ion forms a salt with thepolyanion which then forms a hydrated swollen colloid, but it is notintended that the invention be limited by this or any other theory ofoperation. It has been found essential that the molecular weight of thepolyanion should be between about 350 and 35,000 (viscosity average) andis preferably in the portion of that range from about 1000 to about5000. The molecular weight is extremely important in that if thepolyanion has substantially greater molecular weight than the upperlimit of 35,000, little or no improvement in flow and leveling qualityis obtained.

The polyanion may be that of the polymer obtained by thecopolymerization of an mfi-unsaturated carboxylic acid having a singlepoint of monoethylenic unsaturation or a salt of such an acid withanother monoethylenically unsaturated polymerizable compound whichnormally would produce an insoluble homopolymer. The proportion ofacid-containing units in the copolymer should be from about 40 to about60 mole percent in order to provide adequate solubility of the copolymerin the form of its sodium, potassium, lithium or other alkali metalsalt. Examples of the acid that may be thus copolymerized includeacrylic acid, methacrylic acid, itaconic acid, maleic acid, maleicanhydride, and fumaric acid. Examples of the monomers that can becopolymerized there with include styrene, vinyl toluene, isobutylene,diisobutylene of the formula H CC(CH CH C(CH =CH isoamylene,branched-chain hexenes, dipentene, limonene, terpineol,dicyclopentadiene, esters of any of the acids mentioned above andespecially the esters thereof having from 1 to 18 carbon atoms in thealkyl group, such as the methyl, ethyl, butyl, t-octyl and cctadecylesters of acrylic acid or methacrylic acid (which acid may berepresented by the formula in which n is an integer having a value of 1to 2) or itaconic acid, acrylonitrile, methacrylonitrile, vinyl acetate,vinyl chloride, vinylidene chloride or mixtures of two or more of suchcomonomers.

The salts may be formed by the neutralization of maleic anhydridecopolymers with aqueous ammonia or an alkali metal base. Sinceneutralization (at room temperature up .to 50 C. or even up to about 70C.) of the maleic anhydride copolymers with ammonia produces bothammonium salt group-s and amide groups in proportions correspondingsubstantially to the proportions in which such groups would be presentin the half salt of the half amide of the copolymer, the ammonium saltsof the present invention may be herein designated as an ammonium salteven though the copolymer contains a proportion of the amide groupswhich varies more or less from the strict amount that wouldtheoretically be present if all of the units in the polymer derived frommaleic anhydride were converted to monoamide units. Reference herein tothe amonium salt of the copolymer of maleic anhydride is intended toinclude the salt of the half amide or maleamic acid copolymer which isactually formed.

The polyanion may also be that of lign-in sulfonates having the propermolecular weight defined above. The polyanion may be that of aformaldehyde condensation product of a naphthalene-sulfonic acid or ofalower alkylf substituted naphthalene sulfonic acid in which the alkylsubstitution comprises from 1 to 9 carbon atoms, examples being methyl,ethyl, isopropyl, butyl, hexyl, n-octyL t-octy-l (derived fromdiisobutylene), dodecyl, nonyl (derived from triisopropylene), and soon. The product provides a plurality of sulfonic acid groups sufficientto confer water-solubility on the ammonium, alkali metal orammonium-half amide salts and the number of aryl nuclei connected bymethylene bridges is suficient to provide a molecular weight of at least350. These poly-anionic materials may be made by known procedures suchas by condensing formaldehyde with naphthalene-sulfonic acid or analkylnaphthalene-sulfonic acid or by the methods described in US.Patents 898,307 and 1,336,759. The polyan-ion may also be that of thesulfation or sulfonation or mixed sulfation-sulfonation product of acondensation product of ethylene oxide with the condensation products offormaldehyde with an alkyl-substituted phenol, anaphthol, or fi-naphtholin which the alkyl substitution may comprise from 1 to 24 carbon atoms,examples being methyl, ethyl, isopropyl, butyl, heXyl, n-octyl, t-octyl(derived from triisopropylene), decyl, dodecyl including lauryl andt-dodecyl (derived from triisobutylene), hexadecyl, octadecyl, and soon, the polyanionic material in this case also having a molecular weightwithin the range: specified and having a plurality of sulfate orsulfonate units sutficient to render the ammonium, alkali metal or aminesalts water soluble. The products of this type in clude those of U.S.Patents 2,454,542-3. The polyanion may also be that of theesterification product of a poly-- carboxylic acid, and preferably adibasic acid, such as succinic, glutaric, adipic, phthalic, and maleic,with the ethylene oxide condensation products just mentioned. Theproducts of this type include those of US. Patent 2,454,544. Thepolyanion may also be that of the by drolysis product of the{i-cy-anoethyl ethers obtained by the reaction of acrylonitrile with theethylene oxide condensation products mentioned above. The products ofthis type include those of US. Patent 2,454,545.

The following three formulas illustrate some of the compounds generallydescribed above which may be used to provide the polyanions of thepresent invention:

Ar is a benzene or naphthalene nucleus,

R is a hydrocarbon substituent of at least 4 carbon atoms, andpreferably of 8 to 18 carbon atoms,

R is H or a hydrocarbon substituent of 1 to 18 carbon atoms,

R is H or a hydrocarbon substituent of 1 to 18 carbon: atoms,

R is H or a hydrocarbon substituent of l to 18 carbon atoms,

A is an alkylene group of 2 to 4 carbon atoms and preferably ethylene, V

Y is --SO M, --COOM, or OCOR (COOM) where M is NH or an alkali metal andR i 11 alkyl QI aryl radical of 1 to 7 carbon atoms,

in is O or an integer from 1 to 20,

n is O or an integer from 1 to 20,

x is an integer having a value of 2 to 5 or more, and y is 3 to 5.

Outstanding results are obtained when the sodium, ammonium, or otheralkali metal salt of the copolymer of maleic acid or its anhydride withdiisobutylene is employed to provide the polyanion.

The polyvalent cations that may be introduced are those of calcium,magnesium, barium, strontium, cadmium, copper, mercury, zinc, chromium,and aluminum. These cations may be introduced by the addition of asuthciently soluble salt of the polyvaleut metal. For example, zinc maybe introduced as the zinc acetate, chloride, nitrate, or sulfate, salt;calcium may be introduced as the chloride or sulfate; barium as well asall of the others may be introduced as the chlorides or nitrates. If thehydroxides of the metals are sufiiciently soluble, the polyvalent cationmay be introduced by means of the hydroxide and, when the oxide issufiiciently soluble, the oxide may be used. Calcium oxide issufficiently soluble to be used with both acid and basic dispersions;magnesium oxide and zinc oxide are not sufficiently soluble to be usedin alkaline dispersions, but may be used with dispersions having a pHsubstantially below 7, such as 6.5 or less.

It has been found that the improved flow and leveling of the presentinvention is obtained generally with aqueous dispersions ofwater-insoluble synthetic linear addition polymers. Such polymerdispersions are generally obtained by the emulsion polymerization ofpolymerizable materials, especially those of monoethylenicallyunsaturated character, though butadiene, isoprene, and chlorobutadienemay be used to some extent. Examples of the polymerizable materialsinclude all of the comonomers that were mentioned above for making thepolyanion. Dispersions obtained by the emulsion copolymerization of anytwo or more of these monomeric materials are suitable, provided thecopolymer obtained is of waterinsoluble character. The polymer used asthe binder may also contain a small proportion of units derived frommonomers which normally produce soluble homopolymers. Thus, they maycontain from about A up to 3% of any one or more of such water-solublepolymer-forming materials as acrylamide, any of the acids mentionedabove, such as acrylic acid, methacrylic acid, itaconic acid or maleicacid. Specific examples of polymer binders that may be formed byemulsion polymerization to provide the major part of the aqueous coatingcomposition include polyvinyl acetate, polyvinyl chloride, copolymers ofpolyvinyl acetate with polyvinyl chloride and acrylonitrile, copolymersof vinyl chloride with acrylonitrile or vinylidene chloride,polyethylene, polyisobutylene, copolymers of styrene with butadiene,copolymers of butadiene with acrylonitrile, copolymers of acrylic esterswith each other, such as copolymers of ethyl acrylate with methylmethacrylate and any of the copolymers disclosed in US. Patent2,760,886. The addition polymers here involved are those obtained bywhat may be generically termed vinyl addition or vinyl polymerizationsince the polymers result from the reaction at the points ofunsaturation to yield an essentially saturated linear polymer chain. Forthe purpose of the present invention, the polymer used as the binder mayhave any value of T, from 50 C. up to about 40 C. when application is tobe made at usual conditions of temperature which may be from about 0 C.to about 35 C. or so. The higher the temperature of application, thehigher the T may be in the range cited above. For some specialapplications, where the application of the coating material to thesubstrate is eifected at unusually high temperatures, higher values of Tup to 60 C. or more may be employed. For most practical purposes,however, it is 3 preferred that the T value is no higher than some pointin the range from 20 to 35 C.

One or more plasticizers for the binder polymer may be present in anamount from about 1 to 20% or more by weight of the binder, 5 to 20%being a preferred proportion, when plasticizer is used. Such plasticizerfacilitates coalescence of the polymer particles into a continuous film,especially when application is made at temperatures which are low ascompared to the T of the polymer used. Examples of plasticizers includebutoxyethoxyethyl acetate, dinonyl phthalate, dioctyl phthalate, dioutylphthalate, triphenyl phosphate, Z-etnyl hexyl benzyl phthalate anddicyclohexyl phthalatc. Other well-known plasticizers for polymers ofmethyl methacrylate which may be employed includes diallyl phthalate,dibenzyl phthalate, butyl cyclohexyl phthalate, mixed benzoic acid andfatty oil acid esters of pentaerythritol, poly(propylene adipate)dibenzoate, diethylene glycol dibenzoate, tetrabutylthiodisuccinate,outyl phthalyl butyl glycolate, acetyl tributyl citrate, dibenzylsebacate, tricresyl phosphate, toluene ethyl sulfonamide, the di-2-ethylhexyl ester of hexamethylene diphthalate, and di(methylcyclohexyl)phthalate. About 2 to 5%, on the total weight of the aqueous dispersion,of ethylene glycol, diethylene glycol or the monoalkyl ethers ofdiethylene glycol in which the alkyl group has 1 to 4 carbon atoms maybe included to assure freeze-thaw stability, especially whenplasticizers are included.

The T value referred to is the transition temperature or inflectiontemperature which is found by plotting the modulus of rigidity againsttemperature. A convenient method for determining modulus of rigidity andtransition temperature is described by I. Williamson, British Plastics,23, 87-90, 102 (September 1950). The T, value here used is thatdetermined at 380 kg./crn

In the production of the polymer dispersion by emulsion polymerizationprocedures, a non-cationic emulsifier may be used. Any non-ionicemulsifier may be employed but when an anionic emulsifier is used, itshould be selected so that the addition of the polyvalent metal ionsdoes not cause precipitation or coagulation of the polymer or it shouldbe used in conjunction with a non-ionic emulsifier in sufiicient amountto prevent such coagulation.

Typical non-ionic emulsifiers include alkylphenoxypolyethoxyethanolshaving alkyl groups of about seven to twelve carbon atoms, such asheptylphenoxypolyethoxyethanols, octylphenoxypolyethoxyethanols,methyloctylphenoxypolyethoxyethanols, nonylphenoxypolyethoxyethanols,dodecylpheuoxypolyethoxyethanols and the like; polyethoxyethanolderivatives of methylene linked alkyl phenols; sulfur-containing agentssuch as those made by condensing the required proportion of ethyleneoxide with nonyl, dodecyl, tetradecyl, and the like mercaptans or withalkylthiophenols having alkyl groups of six to fifteen carbon atoms;ethylene oxide derivatives of long chain carboxylic acids, such aslauric, myristic, palmitic, oleic, and the like or mixtures of acidssuch as found in tall oil; ethylene oxide condensates of long-chainedalcohols, such as octyl, decyl, lauryl or cetyl alcohols, ethylene oxidederivatives of etherified or esterified polyhydroxy com pounds having ahydrophobic hydrocarbon chain, etc.

Typical anionic emulsifiers include any or" the compounds of Formulas I,II, and HI hereinabove and also the alkali metal salts of higher fattyalcohol sulfates having 8 to 18 or more carbon atoms.

The amounts of emulsifier or emulsifiers required vary primarily withthe concentration of monomers to be handled and to a minor extent withchoice of emulsifier, monomers, and proportions of monomer. Generally,the amount of emulsifying agent is between 2 and 12% of the weight ofthe mixture of monomers and is preferably 4 to 7% of this Weight. If thedispersion is to contain a relatively low concentration of interpolymersomewhat more than the minimum emulsifying agent indicated by theaqueous polymer dispersion may be lowered.

the above rule may prove desirable. In such case, the concentration ofemulsifying agent in the aqueous solution may desirably be at least 1%of this solution and may be as much as about 7% of the weight of theaqueous solution thereof.

The concentration of the emulsion polymer used as the binder within theaqueous coating system may vary from about 10% to 60%, but is preferablyin the range of about 15 to 55% by weight. The amount of thewatersoluble salt of the polyanion that may be added may vary from about/2 to 10% on the weight of the aqueous phase in the system, and ispreferably about 1 /2 to 5% of the aqueous phase. The aqueous phase hererefers to the water and any water-soluble solvent, such as the glycol,used, but excludes any solid material dissolved or dispersed therein.The amount of the polyvalent cation may vary widely and may be equal to,greater than, or less than the amount that is stoichiometricallyequivalent to the sulfonic acid or carboxylic acid units of thepolyanion. It is not necessary that the full equivalent be used. Anexcess of the polyanion or of the polyvalent metal cation may be presentso that the amount of the polyvalent cation may be anywhere from up toabout 2 /2 times the amount that is equivalent to the amount ofpolyanion present. Generally, if a small proportion of the Water-solublesalt of the polyanion is used (based on the aqueous phase), the amountof polyvalent metal ion should be in the higher part of its range,whereas if there is present a large proportion of the water-soluble saltof the polyanion, the amount of polyvalent metal cation may be in thelower part of its range. A larger excess of the polyvalent metal cationthan mentioned above may be present, but it is preferred to avoid suchan excess in order to avoid undesirable sensitivity to water and heat.

The order of introduction of the polyanion and the polyvalent metalcation is not in general a critical matter though, in some specificinstances, it may be more feasible to add one ahead of the other,whereas in others it might be preferable to add the latter before theformer. It is believed that the polyvalent cation forms a salt with thepolyanion which is of such a character that the polyanion iscross-linked by the cation. When higher concentrations of the polyanionand cation are employed, such as in the upper half of the rangehereinbefore specified, a thixotropic system is frequently formed sothat on standing the aqueous coating composition has a gel-likecharacter, but on stirring it becomes quite fluid and is easily applied.The thixotropic systems have the additional advantages normallyassociated therewith in that it is easier to pick up a greater quantityof the composition on each dip of a brush. Also, the thixotropy assistsin the sealing of pores and gaps in the surface being coated withoutinterfering with the good flow and leveling qualities of the system. Infact, it appears that the thixotropic systems exhibit even better flowand leveling qualities than those which are not thixotropic.

When the polyvalent metal cation forms a water-dispersible salt with thepolyanion, that is, a salt which is either water-soluble orself-dispersible, it has been found that an aqueous dispersion of thepolyvalent metal salt of the polyanion may be formed before theintroduction into the aqueous system to be thickened therewith andessentially the same benefits of improved flow and leveling are obtainedas would be obtained by the introduction into the aqueous polymersuspension of the polyanion and of the cation separately.

When the polyvalent metal cation is added, the pH of It is oftendesirable, as in systems in which the copolymer contains a small amountof carboxyl groups, that the dispersion should have a pH of at least9.0, such as from 9.0 up to about 11.5, and the preferred range is from9.0 to 9.5, in order to have practical stability, especially againstfreeze-thaw cycles. In such cases, whenever the addition of thepolyvalent metal causes the pH to go be'- low about 9.0, an alkalinematerial should be added to compensate for this reduction of pH torestore it at least to a value of 9.0 or to any higher value desired.Suitable alkaline materials for this purpose include alkali metal orammonium hydroxides or carbonates. The adjustment of pH in any of thedispersions by means of these alkaline materials provides an additionalway of modifying the system in respect to viscosity.

While the aqueous coating composition formulated from the emulsionpolymer dispersion, the polyanion and the polyvalent metal cation may beemployed directly as a coating composition without the introduction ofpigments, and the improved leveling and flow properties are obtained insuch systems, the more general practice and the preferred procedure isto incorporate pigments to provide a water-base paint of predeterminedcolor. The pigment may be used in a proportion such that the ratiobetween pigment and binder is from 0.2:1 to 8:1 and is preferably fromabout 1:2 to 4:1.

Pigments suitable for use according to the invention are inorganicpigments, such as, for example, chrome yellows, Prussian blues, andBrunswick greens, titanium pigments, such as titanium dioxide, extendedtitanium pigments (extended with either precipitated or naturalextenders, such as calcium carbonate, alkaline earth sulfates, forinstance, calcium sulfate, barium sulfate and the like), tinted titaniumpigments, titanates such as barium, zinc, lead, magnesium titanates, andthe like. Additionally, other types of inorganic pigments may beincluded, such as zinc sulfide pigments, for instance, zinc sulfide,lithopone, other extended zinc sulfide pigments, such as calcium baselithopone, zinc sulfide, extended with natural extenders, and the like;zinc oxide and antimony oxide, or organic pigments, that is organiccoloring matters which are devoid of sulfonic, carboxylic or otherWater-solubilizing groups. Also for the purposes of this invention, weinclude within theterm pigment other water-insoluble organic coloringmatters such as, for example, the calcium or barium lakes of azo lakedyestuffs. In some cases, of which calcium sulfate is an example, apigment or etxender may be used which has a low solubility but issufiiciently soluble to provide the necessary amount of polyvalent metalions to form a salt with the polyanion which serves to provide theimproved flow and leveling characteristics, as well as serving as apigment and/or as an extender.

In preparing the pigmented compositions of the present invention, thepigment may be introduced into the aqueous copolymer dispersion invarious ways. It may simply be added in dry, finely divided form to thecopolymer dispersion with stirring and/ or more or less grinding ormilling action, the addition being preferably made gradually. Thisprocedure is generally most suitable with high speed mixers, blenders ormills when the copolymer dispersion is relatively dilute, of the orderof 10 to 20% solids concentration without the pigment. Dispersing agentsof non-ionic or anionic types or a mixture of both types should bepresent in the dispersion, or added thereto, before, during, or afterthe pigment addition, in adequate amount to maintain the copolymer indispersed condition and also to disperse the pigment added. .However, inmost instances, it is preferred to disperse the pigment or pigments in asmall amount of water with one or more dispersing agents of the typesjust mentioned before combining the pigment with the copolymerdispersion. This may be effected by adding the pigment gradually to thesmall amount of Water (to which the dispersing agent or agents have beenadded or are simultaneously added with the pigment) while merelystirring during the addition or with a certain amount of grinding ormilling, depending on the ease of dispersibility of the pigment Part ofthe water may be added during the addition of the pgment and/or part maybe added after the pigment has been added. Then the pigment dispersionmay be combined with the copolymer dispersion by adding either one tothe other, preferably gradually, while stirring, and, if necessary,grinding or milling. Whichever procedure is employed, when severalpigments are to be mixed in, they may be added as a dry mixture or 10taining in a finely divided state the pigments, colors, or extenders,such as any suitable commercial dispersing agents which are availablefor this purpose; Wetting agents of non-cationic character, andespecially such non-ionic separately in any order desired. Titaniumdioxide and types as are described hereinabove as emulsifying agentsmany colored pigments demand more water than others for the monomers andin the emulsion polymerization and this is especially true of extenders,examples of which procedures: defoaming agents, including waxes, oils,mininclude barium sulfate, lithopone, calcium carbonate, eral spirits,alkylphenoxyethanols, fatty acid amides, and basic lead carbonate. Whenforming highly conphosphate esters, or a solution of an amine or amidein centrated pastes or dispersions of mixtures of pigments an oil;humectants, such as water-soluble gums, ammoone or more of which haverelatively high water demand nium or sodium polyacrylate of highmolecular weight, and one or more others of which have relatively lowwater glycol laurate, propylene glycol, diethylene glycol, etc.; demand,it is sometimes found that selection of a particuauxiliary thickeners,such as water-soluble gums, waterlar order of addition facitatesdispersion and provides 'a soluble polyacrylates and methacrylates ofhigh molecular more permanently dispersed pigment in the finalpigweight, Water-dispersed starches and proteins, etc.; bacmentedcopolymer dispersion. For example, in some tericides and/or fungicides,such as borax, pentach1oro cases, it may be desirable to add the highWater demand phenols, or mercury compounds; perfume-like materials,pigment or pigments first or after only a portion of the includingneutralizing and masking agents, which are low water demand pigment orpigments have been added used to overcome odors or to impart pleasantand distincso that the completion of the addition of the high water tiveodors; other resinous materials in dispersed forms, demand pigment tothe aqueous medium is accomplished such as alkyd resins, drying oils,coumarone-indene resbefore its consistency or viscosity is markedlyincreased. ins, natural resins, such as copals, to cheapen and extendThe addition of the low water demand pigment or rethe binders of thisinvention, and auxiliary corrosion-inmainder thereof is then made.hibiting agents, such as sodium benzoate, sodium dichro- As theemulsifier used in making the polymer dispermate, guanyl urea phosphate,or sodium nitrite, in an sion, the ammonium or alkali metal salt of anyof the amount of 0.05% to 5%, and most commonly 0.1% to polyanionsmentioned hereinabove may be employed to 0f the dispersed p y etc. theexclusion of any other emulsifier or in addition there- Thecoatingcompositions of the present invention may to, such as in addition to anon-ionic type. Depending be applied to any suitable substrate, whetherit has been upon the amount of such emulsifier used and th fi l dilpainted previously or not and whether or not it is porous tion of thecoating system, additional polyanion may or or non-porous. Suchsubstrates "include Wood, plaster, may not be needed to provide theamount necessary to stone, and other masonry, cement blocks, asbestoscement impart the improved flow and leveling in conjunction ProductsSuch as Shingles, yp board, corkboafd, ith h polyvalent i Lik i hammonium or brous materials, such as wall and ceiling tile, acoustictile alkali metal salt of the polyanions mentioned above may of eitherOrganic, fibrous, or inorganic yp wramics, be employed as the dispersingagent for the pigments. In glass, mfilals, Such s Steel, aluminum,Chromium, Silver, the latter case, the polyanion may be introduced intothe P p Cardboard, Chipboard, t and t t le aqueous polymer dispersionSimultaneously with the pig In the following examples which areillustrative of the mem dispersed thfirewim Again, it may may not beinvention, the parts and percentages are by weight unless necessary toadd more of the polyanion later to provide otherwlse noted: the improvedflow and leveling. Example 1 Various auxiliary materials may also beused in preparing the aqueous dispersions of the present invention.Seven water-base paints are prepared by mixing in a These includedispersing agents for dispersing and mainpony mixer the followingingredients in the order listed:

Pounds A B o D E F G Polyanion Solution 18 36 27 27 27 54 27 Defoamingagent (waxy hydrocarbon-Balab 588) 2 2 2 2 2 2 2 28% Aqueous NHiO 5 5 55 5 5 Methyl ether of t-octylphenoxypolyethoxyethanol 6 6 6 6 6 6 6Water 73 73 2s 2s 2s 40 2s Rutile TiO2 225 225 225 225 225 225 225Calcium carbonate 225. 225 225 225 225 250 225 Diatomaceous silica. 25Ethylene glycol 30 30 '35 35 35 30 35 Butoxyethoxyethylaeetate 10 10 1010 10 1 10 Phenyl mercuric acetate 1 1 1 1 1 1 After pony mixing thirtyminutes, there are added with continued mixing in the order listed, theCaClr being added slowly:

Water I 25% solution in Water of the sodium salt of anoapproximately 1:1mole ratio copolymer of diisobutylene and'maleie anhydride (vise. ave.mol. wt. 2000-450 1 Aqueous dispersion of about 43% of a copolymer ofabout 66% ethyl acrylate, about 32.5% methyl methacrylate, and about1.5% acrylic acid containing about 3% t-octylphenoxypolyethoxyethanoland neutralized to a pH of about 9 with NH4OH.

3 In making A and B, a portion of the water may be withheld and addedafter pony mixing as in the other formulations.

The properties of the seven paints are as follows: are added 10 parts byweight of a 25% aqueous solution A l B C D E F G 65 68 67 70 80 to 6564' Light thixo- Extremely Light Light Light Extremely Viscosity (Krebsunits) tropic gel. thix. stifi thix. thix. thix. thixotropgel. gel. gel.gel. ic.

Ratio CaOlz/maleic copolymer salt 1:1 3:7 6:4 4:6 4:6 4:6 RatioWater/sum of 03.015 and maleic copolymer salt 97. 7:2.3 94.5255 96323.796623.4 96.1:3.9 96:4 Solids (percent by Weight) 62 54 59 60 v 58. 5 7764 Pigment Volume Cone.

(percent) 47 47 47 47 47 52. 5 47 Paint G which lacks the polyvalentcation has high solids, relatively low viscosity and very short wet-edgeor brushing time.

seriously impaired.

When the usual synthetic polymeric thickening agents are added to G inan attempt to improve brushing properties, it is found that the wet-edgetime is only slightly increased but the flow and leveling is Paint F hasa moderately stifi gel structure which breaks down readily upon brushingor roller-coating to give excellent flow and leveling and wet-edge time.

All of the above formulations except G are thixotropic systems whichform reversible gelled structures on standing. All except G exhibitexcellent flow and leveling when applied by brush or roller as well asconsiderably longer wet-edge time than the paints prepared withconventional polymeric thickeners.

All paints have excellent scrub resistance and are stable for at leastone freeze-thaw cycle.

Example 2 The following materials were mixed together in the orderlisted in a pony mixer:

Pounds Defoamer (Balab 588) 2 NH OH (28%) 5 Water 200 25% aqueoussolution of sodium salt of 1 :1 mole ratio copolymer of diisobutyleneand maleic anhydride (vise. ave. mol. wt. 20004500).

The calcium sulfate provides the polyvalent metal cation. The mixture isgiven one pass through a 3-roll mill and there are then mixed into thebatch, in the order listed, the following:

Aqueous polymer dispersion 2 350 Defoamer as above solution in water) 8Ethylene glyc 3O Phenyl mercuric acetate 2 43% aqueous dispersion ofammonium salt of a 'copolymer of about 66% ethyl acrylate, 32.5% methylmethacylate, and about 1.5% acrylic acid containing about 3% oft-octylphenoxypolyethoxyethanol, pHzQ.

Thereby 100 gallons of a white water-base paint is obtained having thefollowing properties:

pl-T 9.3.

Visc. (Krebs units) 67.

Pigment vol. con 53%.

Solids 58%.

Freeze-thaw At least 2 cycles.

Thepaiut has excellent flow and leveling on brush and 60 .rollerapplication. The film has at least 1000 cycles of scrub resistance(Gardner Scrub Test).

An extremely thixotropic gel, which is still reversible, is obtainedwhen additional sodium salt of 1:1 .mole ratio maleicanhydride/diisobutylene copolymer is introduced until the total contentof such salt is 6 to 6.5%, based on the calcium sulfate. The resultingdispersion V has good flow and leveling and the additional property a ofa reversible thixotropic gel structure, V, 7

Example 3 To 100 parts of an aqueous dispersion of about 43% by weightof the same ethyl acrylate copolymer as is 7 used in preceding examples,whichcontains about 3% of t-octylphenoxypolyethoxyethanol as anemulsifier, there .of the sodium salt of the 1:1 mole ratio maleicanhydride/diisobutylene copolymer and 20 parts by weight of a 10%solution in water of calcium chloride, both additions being made slowlywith agitation. Upon the addition of the calcium chloride, a thixotropicgel forms which is reversible in character and has good flow andleveling when applied by brush or roller. The coatings obtained aresubstantially clear and resistant to scrubbing.

Example 4 ing when applied by brush and roller.

Example 5 To parts by weight of a 51% polyvinyl acetate dispersion inwater there are added 10 parts by weight of the same 25% sodium salt ofmaleic anhydride copolymer as is used in the preceding examples and 21parts by weight of a 10% solution of calcium chloride in water. A lightthixotropic gel forms which is reversible in character and providesexcellent flow and leveling on application by brush and roller.

Example 6 To 100 parts of the same aqueous dispersion of ethyl acrylateas is usedin Examples 1 to 4, there are added 10 parts by weight of thesame 25% solution of the sodium salt of maleic anhydride copolymer and33.3 parts of a 10% solution in water of the dihydrate of zinc acetate.Within ten minutes after the addition of the zinc acetate, a thixotropicgel is formed. This gel is reversible and the dispersion obtained hasexcellent flow and leveling on brush and roller application.

Example 7 One hundred and eighty parts of rutile TiO is dispersed in asolution formed of a mixture of 15.6 parts of water and 45 parts of anaqueous solution containing 29% of sodium salt of a copolymer of about60 parts by weight of ethyl acrylate with about 40 parts by weightof'methacrylic acid having a viscosity average molecular weight of about35,000. Then parts by weight of the same 43% ethyl acrylate copolymerdispersion as is used in Examples 1 through 4 is added and mixedthoroughly. Then 40 parts by weight of a 10% aqueous solution of calciumchloride is added slowly with constant stirring and finally anadditional 45 parts by weight of the 29% aqueous solution ofthe sodiumsalt of the ethyl acrylate/ methacrylic acid copolymer initially addedto the rutile TiO is mixed in. Upon the addition of the last salt, athixotropic gel forms and the dispersion has good flow and leveling whenapplied by roller and brush.

Ninety parts of rutile TiO are mixed with 40 parts by weight of a 10%aqueous solution of a sodium lignin sulfonate having a viscosity averagemolecular weight of 1000 to 2000. Then 70-parts by weight of the same46% ethyl acrylate copolymer dispersion as is used in Examples 1 to 4 isadded with continued mixing. Finally, 30 parts by weight of a 10%aqueous solution of calcium chloride is added slowly with constantagitation. A thixotropic gel of reversible character is formed. Thedispersion exhibits good' flow and leveling on application by brush androller.

Example 9 To 300 parts by weight of the same 46% ethyl acrylatecopolymer dispersion as is used in Examples 1 to 4, 45 parts by weightof an approximate 18% solution of the sodium sait of a condensationproduct of naphthalenesulfonic acid with formaldehyde having a viscosityaverage molecular weight of about 1000. Thereafter about 12 parts of a10% aqueous solution of calcium chloride is added slowly with mixing andfinally three parts by weight of a 28% aqueous ammonia solution isadded. A reversible thixotropic gel structure is obtained. Thedispersion has good flow and leveling when applied by brush and roller.

Example 10 Example 11 There are mixed with agitation the followingsubstances in the order and amounts named:

Parts by weight Rutile TiO 90 Polyanion solution 1 7.2 Water 25 Aqueouspolymer dispersion 2 70 1 Sodium salt of 1 :1 mole ratio copolymer ofmaleic anhy dride and diisobutylene having a viscosity average molecularweight of 20004500 (25% solution in water).

2 Aqueous dispersion of about 43% of a copolymer of about 66% ethylacrylate, about 32.5% methyl meth-acrylate, and about 1.5% acrylic acidcontaining about 3% of tctylphenoxypolyethoxyethanol and neutralized toa pH of 7.0 with NHiOI-I.

The composition obtained has a stifi gel structure and is quitethixotropic. It has good flow and leveling properties when applied bybrush and roller.

We claim:

1. A composition comprising an aqueous dispersion of a water-insolublesynthetic linear addition polymeric material, said aqueous dispersioncontaining to 60% by weight of said polymeric material, said polymericmaterial being a polymer obtained by vinyl polymerization ofmonoethylenically unsaturated molecules, and a thickening agent which isthe salt of (1) the polyanions of a water-soluble salt of an additioncopolymer of about 40 to about 60 mole percent of ana,,6-monoethylenically unsaturated carboxylic acid with at least oneother monoethylenically unsaturated comonomer which normally wouldproduce an insoluble homopolymer, the copolymer Aluminum sulfate havinga viscosity-average molecular weight of 350 to 35,000 and (2) polyvalentmetal cations, the amount of the water-soluble salt being in the rangeof /2% to 10% or" the wcight'of the aqueous phase, and the amount of thecations being from about one-fifth to two and onehalf times theequivalent weight of the polyanions, and an emulsifier selected from thegroup consisting of anionic and non-ionic emulsifiers.

2. A composition comprising an aqueous dispersion of a water-insolublesynthetic linear addition polymeric material, said aqueous dispersioncontaining 10 to 60% by weight of said polymeric material, saidpolymeric material being a polymer obtained by vinyl polymerization ofmonoethylenically unsaturated molecules, and a thickening agent which isthe salt of 1) the polyanions of a water-soluble sodium salt of acopolymer of 40 to 60 mole percent of maleic anhydride withdiisobutylene having a viscosity-average molecular Weight of 350 to35,000, and (2) calcium cations, the amount of the water-soluble saltbeing in the range of /2% to 10% of the weight of the aqueous phase, andthe amount of the cations being from about one-fifth to two and onehalftimes the equivalent weight of the polyanions, and an emulsifierselected from the group consisting of anionic and non-ionic emulsifiers.

3. A composition comprising an aqueous dispersion of a Water-insolublesynthetic linear addition polymeric material, said aqueous dispersioncontaining 10 to 60% by weight of said polymeric material, saidpolymeric material being a polymer obtained by vinyl polymerization ofmonoethylenically unsaturated molecules, and a thickening agent which isthe salt of (1) the polyanions of a water-soluble ammonium salt of acopolymer of 40 to 60 mole percent of maleic anhydride withdiisobutylene having a viscosity-average molecular weight of 350 to35,000, and (2) calcium cations, the amount of the water-soluble saltbeing in the range of /z% to 10% of the Weight of the aqueous phase, andthe amount of the cations being from about one-ifth to two and onehalftimes the equivalent Weight of the polyanions, and an emulsifierselected from the group consisting of anionic and non-ionic emulsifiers.

4. A composition comprising an aqueous dispersion of a water-insolublesynthetic linear addition polymeric material, said aqueous dispersioncontaining 10 to 60% by weight of said polymeric material, saidpolymeric material being a polymer obtained by vinyl polymerization ofmonoethylenically unsaturated molecules, and a thickening agent which isthe salt of (1) the polyanions of a water-soluble sodium salt of acopolymer of 40 to 60 mole percent of maleic anhydride withdiisobutylene having a viscosity-average molecular weight of 350 to35,000, and (2.) zinc cations, the amount of the water-soluble saltbeing in the range of /2% to 10% of the weight of the aqueous phase, andthe amount of the cations being from about one-fifth to two and one-halftimes the equivalent weight of the polyanions, and an emulsifierselected from the group consisting of anionic and non-ionic emulsifiers.

5. A composition comprising an aqueous dispersion of a water-insolublesynthetic linear addition polymeric material, said aqueous dispersioncontaining 10 to 60% by weight of said polymeric material, saidpolymeric material being a polymer obtained by vinyl polymerization ofmonoethylenically unsaturated molecules, and a thickening agent which isthe salt of (1) the polyanions of a water-soluble salt of an additioncopolymer, having a viscosity average molecular weight of 350 to 35,000,of 40 to 60 mole percent of methacrylic acid with an ester of an acidhaving the formula in which n is an integer having a value of l to 2,with an alcohol having 1 to 18 carbon atoms, and (2) calcium cations,the amount of the water-soluble salt being in the range of /2 to 10% ofthe Weight of the aqueous phase, and the amount of the cations beingfrom about one-fifth to two and one-half times the equivalent Weight ofthe polyanions, and an emulsifier selected from the group consisting ofanionic and non-ionic emulsifiers.

6. A composition comprising an aqueous dispersion of a water-insolublesynthetic linear addition polymeric material, said aqueous dispersioncontaining 10 to 60% by weight of said polymeric material, saidpolymeric material being a polymer obtained by vinyl polymerization ofmonoethylenically unsaturated molecules, and a thickening agent Which isthe salt of (1) the polyanions of a water-soluble sodium salt of anaddition copolymer, having a viscosity-average molecular weight of 350to 35 ,000, of 40 to 60 mole percent of methacrylic acid with ethylacrylate, and (2) calcium cations, the amount of the water-soluble saltbeing in the range of /2% to 10% of 16 the weight of the aqueous phase,and the amount of the cations being from about one-fifth to two andone-half times the equivalent weight of the polyanions, and anemulsifier selected from the group consisting of anionic and non-ionicemulsifiers.

References Cited in the file of this patent UNITED STATES PATENTS

1. A COMPOSITION COMPRISING AN AQUEOUS DISPERSION OF A WATER-INSOLUBLESYNTHETIC LINEAR ADDITION POLYMRIC MATERIAL, SAID AQUEOUS DISPERSIONCONTAINING 10 TO 60% BY WEIGHT OF SAID POLYMERIC MATERIAL, SAIDPOLYMERIC MATERIAL BEING A POLYMER OBTAINED BY VINYL POLYMERIZATION OFMONETHYLENICALLY UNSATURATED MOLECULES, AND A THICKENING AGENT WHICH ISTHE SALT OF (1) THE POLYANIONS OF A WATER-INSOLUBLE OF AN ADDITIONCOPOLYMER OF ABOUT 40 TO ABOUT 60 MOLE PERCENT OF ANA,B-MONOETHYLENICALLY UNSATURATED CARBOXYLIC ACID WITH AT LEASZT ONEOTHER MONOETHYLENICALLY UNSATURATED COMONOMER WHICH NORMALLY WOULDPRODUCE AN INSOLUBLE HOMOPOLYMER, THE COPOLYMER HAVING AVISCOSITY-AVERAGE MOLECULAR WEIGHT OF 350 TO 35,000 AND (2) POLYVALENTMETAL CATION, THE AMOUNT OF THE WATER-SOLUBLE SALT BEING IN THE RANGE OF1/2% TO 10% OF THE WEIGHT OF THE AQUEOUS PHASE, AND THE AMOUNT OF THECATIONS BEING FROM ABOUT ONE-FIFTHE TO TWO AND ONEHALF TIMES THEEQUIVALENT WEIGHT OF THE POLYANIONS, AND AN EMULSIFIER SELECTED FROM THEGROUP CONSISTING OF ANIONIC AND NON-IONIC EMULSIFIERS.